A liposome vesicle encapsulates a region of aqueous solution inside a hydrophobic membrane; dissolved hydrophilic solutes cannot readily pass through the lipids. Hydrophobic chemicals can be dissolved into the membrane, and in this way liposome can carry both hydrophobic molecules and hydrophilic molecules.
Several CFs (Compressed Fluid) methodologies have been used to generate vesicles, some of them already existed and others were developed for this specific application. Most of the methods involve a mixture between the compressed CO2, the vesicle membrane constituents and an organic solvent for producing the vesicles upon contact with an aqueous phase.
Depending on the role of the compressed CO2 used in each method, they can be classified as: Process involving the use of CO2 as a solvent (e.g. Supercritical Liposome Method and Rapid Expansion of Supercritical Solutions), Processes involving the use of CO2 as an antisolvent (e.g. Gas Antisolvent Precipitation and Aerosol Solvent Extraction System) and Processes involving the use of CO2 as a co-solvent or a processing aid (e.g. Depressurization of an Expanded Liquid Organic Solution-Suspension and Supercritical Reverse Phase Evaporation).
Model hydrophilic and hydrophobic compounds, such as fluorescent dyes, sugars and cholesterol, have been encapsulated into vesicles using these methodologies whereas biomolecules like proteins, anticancer drugs and antibiotic, have been integrated in less extent.
Transdermal delivery systems (TDS) were introduced onto the US market in the late 1970s), but transdermal delivery of drugs had been around for a very long time. There have been previous reports about the use of mustard plasters to alleviate chest congestion and belladonna plasters used as analgesics. The mustard plasters were homemade as well as available commercially where mustard seeds were ground and mixed with water to form a paste, which was in turn used to form a dispersion type of delivery system.
Once applied to the skin, enzymes activated by body heat led to the formation of an active ingredient (allyl isothiocyanate). Transport of the active drug component took place by passive diffusion across the skin—the very basis of transdermal drug delivery.
The epi-dermis undergoes changes in structure and function which result in many of the characteristics of aged skin, including loss of elasticity, formation of wrinkles, loss of water-holding capacity, sagging, and poor microcirculation. At the molecular level, these changes have been correlated with biochemical changes in the content and structure of the extracellular matrix to which the major cells of the epi-dermis (i.e., the fibroblasts) reside. Collagen becomes highly cross-linked and inelastic, elastin is reduced in amounts and is incorrectly distributed, which results in reduced intercellular water for reduction and repair of these changes. Nonsurgical options include chemical peels and chemicals with minor irritant properties (e.g., topical retinoid, salicylic acid, and alpha-hydroxy acids), are based on the principle of wounding the stratum corneum—the skin's primary defense against the transit of exogenous materials into the epidermis and dermis—to allow the penetration of constituents through the disrupted skin, which stimulates the desired response, typically restorative healing. All of these techniques require a wound healing response to the skins being intentionally wounded as a method to initiate the rejuvenation process.
Owing to the selective nature of the skin barrier, only a small pool of ingredients can be delivered non-systemically or systemically at therapeutically relevant rates. Besides great potency, the physicochemical ingredient characteristics often evoked as favorable for percutaneous delivery include moderate lipophilicity and low-molecular-weight. However, a large number of skin damage mitigating active agents do not fulfill these criteria.
Chemical permeation enhancers facilitate drug permeation across the skin by increasing drug partitioning into the barrier domain of the stratum corneum, increasing drug diffusivity in the barrier domain of the stratum corneum or the combination of both (2).
The heterogeneous stratum corneum is composed of keratin ‘bricks’ and intercellular continuous lipid ‘mortar’ organized in multilamellar strata (3)(4)(5). Depending on the nature of the drug or ingredient, either of these two environments may be the rate-limiting milieu (barrier domain) for the percutaneous transport.
As a consequence, it is anticipated that the magnitude of permeation improvement obtained with a given permeation enhancer will vary between lipophilic and hydrophilic ingredients. Several mechanisms of action are known: increasing fluidity of stratum corneum lipid bilayers, extraction of intercellular lipids, increase of ingredient's thermodynamic activity, increase in stratum corneum hydration, alteration of proteinaceous corneocyte components and others.
The stratum corneum is a formidable barrier to exogenous agents including cosmeceutical ingredients. Therefore, it is often necessary to add permeation-enhancing chemicals to aid beneficial constituents in passing through the stratum corneum. Permeation-enhancing chemicals include fatty acids, organic solvents (i.e., acetone and ethanol), alcohols, esters and surfactants.
It is generally understood that for enhancers, increased potency is directly correlated with increased skin irritation. Difficulty in reducing the irritation of these agents has been expressed since the same mechanisms responsible for increasing permeation cause irritation. While potent enhancers are effective at transiently compromising the integrity of the stratum corneum barrier, their action is not entirely limited to the stratum corneum and the interaction with viable epidermis can cause cytotoxicity and irritation. Published methods for reducing the skin irritation of permeation enhancers include combining permeation enhancers (synergistic mixtures) and manipulation of their chemical structures.
Conventional lipid or niosome vesicle production techniques have drawbacks such as complex and time consuming procedures involving organic solvents. For liposomes, conventional methods can involve harsh conditions that result in denaturation of the lipids and active ingredients, and also cause poor ingredient encapsulation efficiency.
Since the liposomes were first used as drug carriers in 1970s. Many methods, such as Supercritical fluids (SCFs), for preparing liposomes have been developed, but these methods require large amounts of organic solvents like chloroform, ether, freon, methylenechloride and methanol that are harmful to the environment and the human body, and very few methods have been developed that yield liposomes that have a high trapping efficiency for water soluble substances without using any organic solvent.
Additionally, all these methods are not suitable for mass production of liposomes because they consist of many steps. With the advent of Green Chemistry in the early 1990s, the surge of supercritical fluids (SCFs) increased vastly.
The supercritical state of a fluid (SCF) is intermediate between that of gas and liquids. The SCF has been used widely in pharmaceutical industrial operations including crystallization, particle size reduction, drug delivery preparation, coating and product sterilization. In the pharmaceutical field, supercritical carbon dioxide (scCO2) is by far the most commonly used gas, which can become supercritical at conditions that are equal or exceed its critical temperature of 31.1° C. and its critical pressure of 7.38 Megapascals (Mpa).
The encapsulation degree of any drug into vesicles is influenced by several parameters related to the: a) vesicle composition, b) the nature of the cosmeceutical ingredient and c) the preparation methodology. Regarding the vesicle composition, besides the selection of the lipids forming the membrane and the presence of charges on it, the type of vesicle plays also an important role. Thus, for hydrophilic drugs, such as proteins or peptides, the encapsulation degree appears to increase in the following order: MLV<SUV<LUV. (FIG. 1.0) Nevertheless in the case of hydrophobic drugs, the size and type of liposomes do not seem to play a major role.
Liposomes with a single bilayer are known as unilamellar vesicles (UV). UVs may be made extremely small (SUVs) or large (LUVs) (FIG. 3.0). Liposomes are prepared in the laboratory by sonication, detergent dialysis, ethanol injection, French press extrusion, ether infusion, and reverse phase evaporation.
These methods often leave residuals such as detergents or organics with the final liposome. From a production standpoint, it is clearly preferable to utilize procedures which do not use organic solvents since these materials must be subsequently removed.
Some of the methods impose harsh or extreme conditions which can result in the denaturation of the phospholipid raw material and encapsulated ingredients. These methods are not readily scalable for mass production of large volumes of liposomes.
Several methods, such as energy input in the form of sonic energy (sonication) or mechanical energy (extrusion), exist for producing MLVs (multilamellar vesicles), LUVs and SUVs without the use of organic solvents.
MLVs (multilamellar vesicles), free of organic solvents, are usually prepared by agitating lipids in the presence of water. The MLVs are then subjected to several cycles of freeze thawing in order to increase the trapping efficiencies for water soluble ingredients.
MLVs are also used as the starting materials for LUV and SUV production. One approach of creating LUVs, free of organic solvents, involves the high pressure extrusion of MLVs through polycarbonate filters of controlled pore size. SUVs can be produced from MLVs by sonication,
French press or high pressure homogenization techniques. High pressure homogenization has certain limitations. High pressure homogenization is useful only for the formation of SUVs. In addition, high pressure homogenization may create excessively high temperatures.
Contrary to the present embodiment, extremely high pressures are associated with equipment failures. High pressure homogenization does not insure end product sterility. High pressure homogenization is associated with poor operability because of valve plugging and poor solution recycling.
The use of liposomes for the delivery and controlled release of therapeutic drugs requires relatively large supplies of liposomes suitable for in vivo use (FIG. 6.0). Present laboratory scale methods lack reproducibility, in terms of quantity and quality of encapsulated ingredients, lipid content and integrity, and liposome size distribution and captured volume.
The multidimensional characteristics of the ingredient and the liposome, as well as potential raw material variability, influence reproducibility. Present state-of-the-art liposome and niosome products are not stable. It is desirable to have final formulations which are stable for six months to two years at room temperature or at refrigeration temperature.
Present liposome products are difficult to sterilize. Sterility is currently accomplished by independently sterilizing the component parts lipid, buffer, ingredient and watery autoclave or filtration and then mixing in a sterile environment.
This sterilization process is difficult, time consuming and expensive since the product must be demonstratively sterile after several processing steps. Heat sterilization of the finished product is not possible since heating liposomes or niosomes does irreparable damage. Filtration through 0.22 micron filters may also alter the features of multilayered liposomes and elastic niosomes.
Gamma ray treatment, not commonly used in the pharmaceutical industry, may disrupt liposome or elastic niosome membranes. Picosecond laser sterilization is still experimental and has not yet been applied to the sterilization of any commercial pharmaceutical.
In the past two decades, several cosmetic formulations based on ingredient delivery systems have been successfully introduced for the treatment of skin disorders. Many problems exhibited by free active cosmetic ingredients (ACIs), such as poor solubility, toxicity, rapid in vivo breakdown, unfavorable pharmacokinetics, poor bio distribution and lack of selectivity for target tissues can be ameliorated by the use of a VDS (vesicle delivery system) as offered by the current embodiment. Although a whole range of delivery agents exist nowadays, the main components typically include a nanocarrier, a targeting moiety conjugated to the nanocarrier, and a cargo, such as the desired cosmeceutical ingredient.
In 1846, Gobley separated phospholipids from egg yolk. The term “lecithin” which is derived from the Greek lekithos was first used to describe a sticky orange material isolated from egg yolk. “Lecithin” refers to the lipids containing phosphorus isolated from eggs and brains; (3) from a scientific point of view, “lecithin” refers to PCs (phosphatidylcholine) the most common phospholipid, egg yolks, liver, wheat germ and peanuts contain the phospholipid lecithin.
Phospholipids (FIG. 3.0) have excellent biocompatibility. In addition, phospholipids are renowned for their amphiphilic structures. The amphiphilicity confers phospholipids with self-assembly, emulsifying and wetting characteristics. When introduced into aqueous milieu, phospholipids self-assembly generates different super molecular structures which are dependent on their specific properties and conditions.
In the need for synthetic analogs of natural phospholipids, further synthetic phospholipids were for instance designed to optimize the targeting properties of liposomes. Examples are the PEG-ylated phospholipids and the cationic phospholipid 1,2-diacyl-P-O ethylphosphatidylcholine. Also attempts were made to convert by organic chemical means phospholipids into pharmacological active molecules (for instance ether phospholipids or to make phospholipid pro-drugs.
DPPC is the major constituent of stratum corneum surfactants which controls the dynamic surface tension (DST) and helps maintaining the epi-dermis health. It is also one of the most popular phospholipids used for preparing lipid or niosome bilayers and model biological membranes.